Download Elana McDermott Final Paper Global Coral Reefs: Concerns

Elana McDermott
Final Paper
Global Coral Reefs: Concerns, Developments, and Preservation Efforts
The preservation of our natural resources has taken high national and global importance during the
last few decades. Our world and resources are easily impacted by human interactions. While scientific
research continues to produce new methods for conserving our national resources, many global ecosystems
have already been critically damaged by human actions. One such ecosystem that is in desperate need of
large global conservation efforts are the coral reefs.
For centuries, coral reefs have provided a multitude of resources. These areas serve as breeding
grounds for fish and other wildlife and are home to many varieties of marine plant life. These reefs not only
protect and produce marine life, but they also provide food and economic stability for the countries
surrounding these natural wonders. However, it is because of the multitude of uses coral reefs provide that
an estimated 30 percent of the world’s coral reefs are severely damaged. What is even more astonishing is
that this number will have doubled by the year 2030 (Hughes et al. 2003). This damage is primarily caused
by human interactions with the ecosystem. The decline of this fragile environment is a crisis both locally
and globally. Locally, reefs are damaged by overfishing and the exploitation of corals inside the reefs and
in surrounding areas. Globally, the increase of carbon dioxide emissions combined with terrestrial runoff
have created an enormous decline in water quality. Climate changes caused by global warming are
responsible for the increased bleaching of corals and more frequent occurrences of disease in coral
populations.
This natural resource is being rapidly diminished, but there still remains hope for the future of reef
ecosystems through scientific research and discovery. In this paper I will discuss issues of reef conservation
efforts in order to provide a detailed view of the current state of the world’s coral reefs.
Negative human impact on reef ecosystems has historically appeared in the forms of overfishing
and pollution. While these two factors have played a large role in the degradation of global reef ecosystems,
in more recent years the impact of disease and coral bleaching has become as important in the eyes of the
scientific community. Although all of these problems are significant, the factors responsible for reef
ecosystem decline are undermined by the severe lack of information pertaining to the historical sequence of
reef degradation. Scientists were unable to study the impact of these factors with out an accurate historical
record of reef degradation throughout human history. Pandolfi et al. (2003) set out to determine a practical
and relevant timeline of degradation in various reef ecosystems. Through the use of 7 general categories of
biota and 7 defined periods from the history of humanity, the scientists were able to reconstruct the
ecological histories of 14 coral reef ecosystems world wide. Ranging from prehuman to present the time
periods were distinctly separated by human advances in technology and economic development. These
factors are known to create substantial impact on surrounding reef environments.
The constructed historical timelines for reef degradation showed sharp ecological degradation in
the reefs, especially in large and free-living animal populations. The researchers used principal components
analysis to organize the data and display the ecological status of the reefs in a linear fashion. This showed
that there was significant damage from human activities before the year 1900. This is primarily attributed to
over fishing and possibly from land derived pollution. The data showed the western Atlantic as having the
most severe decline. What was most shocking was that although the Great Barrier Reef, the most protected
reef in the world, is closest to pristine conditions, it is still over one third of the way to ecological extinction.
The timeline is a powerful tool in explaining global patterns and causes of ecosystem decline and
collapse. According to the timelines, if radical human intervention and protection does not take place in the
near future reef ecosystems will not survive more than a few more decades. The patterns found in the data
will provide scientists with an accurate means by which to measure future degradation and conservation.
The problems facing the coral reefs are as abundant as they are diverse. Historically, widespread
damage from human impactt has predominantly come from over fishing, agricultural and urban
development, and the resulting runoff pollution caused by this development. The major decline in local
populations of herbivorous fish because of overfishing has led to the increase of seaweeds and the
consequent decrease or coral populations. While overfishing has long been a cause for coral reef decline,
the most recent problems challenging this ecosystem are the effects of global climate changes. Global
climate changes are the cause of a number of problems such as changes in ocean chemistry, increased
frequency and intensity of hurricanes, and the increased spread of disease and coral bleaching. New studies
show that there have been rapid fluctuations in climate throughout history. After viewing historical records
of past climate changes, Hughes et al. 2003 say, it is to be expected that the reefs will be affected by the
changing temperatures on both local and global scales. Although these corals have survived fluctuations in
temperature before, the researchers are certain that the increase of carbon dioxide in the atmosphere will
not only speed up this process, but that the temperatures will far exceed any previous conditions. There are
two primary differences between climate changes of the past and the current change we are facing. The first
is that historically when temperatures increased the sea level rose as well, however it is projected that in the
next hundred years the sea level will raise a relatively small amount. The second is that due to human
interference many of the reefs have been fragmented, making them far more susceptible to climate change
and disease. Combined, these circumstances provide a bleak outlook for the future of reef ecosystems.
The ocean plays an important role in regulating the level of carbon dioxide in the atmosphere.
Since the industrial revolution, the level of carbon dioxide emissions has grown exponentially, resulting in
larger amounts of gas being absorbed by the ocean. This has changed the ocean’s chemistry by increasing
the acidity of the water and has also decreased the water’s capacity to continue absorbing the gas. The
decrease in ocean pH and the increase in carbonate saturation could have tremendous impacts on calcifying
marine biota; as carbonate supersaturation effects calcification rates. Normally, reef waters are naturally
renewed by ocean currents, but because of lowered water levels from global warming, reef waters are
unable to be replenished by fresh ocean waters. This creates vast areas in which the water is not only
stagnant but extremely rich in carbon dioxide causing over calcification, further lowering the pH of the
waters.
Using an almost three hundred year old coral Pelejero et al. (2005) were able to reconstruct the
history of seawater pH during the last three centuries. In order to obtain this information the full length of
the coral was sampled in five year increments. This information provided a continuous record of the acidity
of the seawater based on the boron isotropic composition of the coral. It is now believed that there is a 50
year cycle for oceanic pH levels.
Because levels of oceanic acidity vary all over the globe, local atmospheric conditions could cause
large variations in how a reef responds to this change. From this research scientists determined that corals
are resilient to short term changes in seawater pH. However, due to global climate changes and prolonged
exposure to carbon dioxide, corals may be facing unprecedented low levels of pH. This research could
provide valuable information for responses to increased ocean acidification in the future.
Global climate change also affects weather patterns. There has been a rise in not only the intensity
of tropical storms and hurricanes but also in the frequency with which they occur. Because of this increase,
it is believed that reefs will not have ample time to recover between each storm. The most recent large scale
natural disaster effecting coral reef ecosystems was the December 2004 tsunami in the Indian Ocean.
Following the disaster, scientists feared the worst for these coral reefs. The powerful wave was capable of
carrying vast quantities of pollutants, debris, and sediment over the coral reefs, potentially wiping most of
them out. Fortunately many of the reefs off the coast of Thailand were spared. After evaluating 175 sites in
the Andaman Sea, researchers determined that only 13 percent of them were severely damaged; remarkably,
40 percent appeared to be untouched.
As researchers and volunteers gathered to determine the extent of the damage they also attempted
to aid in the rapid recovery of the reefs. Sand and rubble covered many corals but much of the silt and mud
washed past the reefs and out to sea. Large debris that were swept into the ocean as the tsunami retreated
included logs, beach beds, towels, palm trees, boat engines, and beach umbrellas. Most often, these objects
simply plowed through the reef corals. In an attempt to salvage the remaining reefs, volunteers worked to
upright corals that had been knocked over and removed debris. It is believed that these sites damaged by
the tsunami should recover within five to ten years.
In other sites off of Thailand and India the reefs were devastated by the powerful wave, where 3
out of 4 reefs that were surveyed were destroyed. Divers in these areas measured up to 5 millimeters of silt
and sediment on top of the corals. It is unknown whether or not these reefs will be able to recover from the
damage caused by the tsunami, and researchers believe it will take time before they can more accurately
measure the damage that was incurred during the disaster (Pennisi 2005). Disasters like this, though
unavoidable, have an irreversible effect on an already fragile and limited resource.
The spread of coral bleaching and disease has a devastating impact on marine ecosystems. Coral
bleaching is a naturally occurring problem that is increased in its severity by rising climate temperatures..
During bleaching the corals expel their zooxanthellae which, under normal circumstances, live in a
symbiotic relationship with the coral and provide the corals’ coloring. When they are expelled, the
zooxanthellae leave the coral pale or white in color. This bleaching is a stress response to increased water
temperatures. If the temperature remains too high for the coral to resume normal symbiotic functions it
often leads to high mortality and reduced growth rates. Currently, water temperatures are rising too rapidly
for the corals to acclimate or evolve. Corals are prone to slower evolutionary changes because of
overlapping generations and high levels of asexual reproduction. However, a coral reef will undergo
dramatic changes in order to survive climate changes.
One characteristic of corals that may help preserve reef ecosystems is their ability to migrate in
response to environmental changes. During past periods of temperature fluctuation many species of coral
migrated quickly to more agreeable temperatures through asexual reproduction. This affects the community
structure as corals migrate away from their existing locations, effectively expanding the reach of the reef. If
the corals manage to stay functionally connected to each other they are more likely to be resilient after
recurrent bleaching. This is because they are then able to repopulate the destroyed areas through both
spawning and asexual reproduction. However, many reefs around the world have become isolated because
of both human interference and severly increased water temperatures. If these isolated corals cannot adapt
to the temperature changes they will inevitably be destroyed.
New methods for preserving the coral reef ecosystem have emerged because of this rapid
degradation. In order to protect these areas it has become vital to understand more about how the ecosystem
functions, as a whole and on smaller levels. An ecosystem is structured by how the resources available are
partitioned to each species and how abundant each species is within that community. In order to predict the
consequences of habitat loss, it is critical to understand how the abundance of a species in a community
will affect the resource partition. In working with marine ecosystems a rare species may be represented by
as few as one individual. Connolly et al. (2005) attempted to demonstrate the characteristic patterns for
community and habitat development in two biologically diverse marine systems. The study was
orchestrated to show numerical abundance and resource use in 2 marine systems. The first was the “biodiverse” Central Indo-Pacific and the second the relatively “depauperate” reefs off of French Polynesia.
Scleractinian corals, hard corals which are the main building blocks of a coral reef, and labrid fishes which
are known as the primary consumers in a reef ecosystem were particularly important in determining the
ways in which resources are used and how structure is formed in the ecosystem.
Through their observations the researchers began to get a broader notion of the extent of the
marine life existing in each ecosystem. Connolly et al. (2005) determined that the corals were constrained
by a relatively small set of resources, but that the fishes were able to partition the available resources in
many more ways. The authors stated that species abundance springs from the general consequences of
environmental probability
The study supports the idea that community structure is based upon the Central Limit Theorem in
which abundance distributions among species arise as the consequence of the multiple interactions between
the ecological factors that affect population growth. While this theory is controversial it allows for the
proper integration of probable environmental factors when calculating the abundance levels of each species.
Essentially, the researchers could not provide an accurate method for calculating species abundance. They
do, however, fear that with the rapid destruction of this delicate ecosystem scientists will not be able to
adequately study “the spectrum of environmental variability to which coral reef organisms are exposed”.
In recent years research responding to problems of coral bleaching and overfishing has emerged
with the potential to help preserve this vital natural resource. Following this pattern is believed that greater
understanding of the potential flexibility of the symbiotic relationship between corals and zooxanthellae
may help preserve reef ecosystems globally. At Magnetic Island, an inshore reef in the central section of
the Great Barrier Reef, researchers studied 2 types of spawning corals- Acropora tenuis and A. millepora,
focusing specifically on two strains of Symbiodinium; strain C1, known for fast reproduction and greater
contribution of nutrients to the host, and strain D which has a higher thermal tolerance. The genetically
diverse nature of zooxanthellae influence the physiological properties and tolerance of reefs to disturbance.
Identifying each zooxanthellae and its specific relationship with the coral reef habitat could be vital in
determining the stability prosperity of global coral reefs.
Juvenile populations initially harbored both Symbiodinium C1 and D. Although the corals grew
over two times faster when they were introduced to Symbiodinium C1 in the fourth month, Symbiodinium D
took a clearly dominant role in the juvenile populations. Researchers believe that this difference indicates
the active selection of the symbiont for the changing needs of the coral as it matures. The selection of strain
D may indicate the distinct physiological needs of the corals which begin to recruit into populations during
the summer months. Due to the adaptability of the corals to new strains of zooxanthellae, the researchers
believe that it is possible to introduce more resilient strains of zooxanthellae to bleached corals in order to
preserve endangered areas. This discovery holds the potential to protect and cultivate global coral reefs that
are more resistant to changes in environment.
As coral populations decrease around the world, scientists are searching for new information of
how these corals have survived for centuries. Coral reefs are known for their genetic diversity and the
complex reef ecosystem that they maintain. The diversity of these reef building corals in enhanced through
the evolution of unprecedented hybrid corals. By analyzing the DNA sequence variation in three species of
Caribbean Acropora the researchers were able to prove the existence of a hybrid coral. Nuclear data from
the genetic tests indicates that A. cervicornis and A. palmata are genetically distinct, but that the third
species, A. prolifera is actually a first generation hybrid. The A. prolifera all contained one allele from each
of the two species’ clades. While allele A was exclusive to A. cervicornis and allele B was exclusive to A.
palmata allele B’ was shared between the two suggesting either a shared ancestral allele or an introgressed
allele from a recent historical hybridization. Opportunities for the creation of hybrid species are provided
through synchronized mass spawning events that are typical of coral species. The existence of these hybrid
species promotes the idea of reticulate evolution or the genetic recombination of diverse interbreeding
populations.
The mitochondrial DNA was not only passed from the two original species to the hybrid species
but it was also passed to the original species through the backcrossing of A. cervicornis with hybrid A.
prolifera. The researchers discovered that coral morphology is extremely sensitive to the nuclear genetic
effects and also to nuclear-cytoplasmic interactions within the nuclear genome of the hybrid based on the
marked difference in appearance in the two hybrid morphotypes.
The hybrid species is capable of cloning by fragmentation showing the potential of this hybrid
species for longevity. This fact will undoubtedly help in the ecological persistence of the species. It will
also promote the prosperity of the coral reef through the formation of rare backcrossing and the
diversification of the species.
Marine protected areas have emerged as the most widely utilized method for preserving and
managing the world’s reefs. These areas are officially no-take zones in which it is prohibited to fish or
remove any species from the ocean, providing a safe haven for many species of marine life. Under ideal
circumstances the areas would increase not only marine life inside the protected waters but also increase
fish stocks in the adjacent areas through natural species and larvae movement.
This type of preservation is still in its infancy as far as scientific research and evidence is
concerned. There are very few reserves that are large, old, or effective enough in which to study the impact
of this method of preservation on large predators. One of the few reserves that meet these qualifications is
the Exuma Cays Land and Sea Park (ECLSP). Located near the center of the Bahamas, there has been an
enforced ban on fishing in this area since 1986.
Contrasting results from in and around the reserve areas. Researchers found that within the reserve
the overall biomass of parrotfish predators was approximately double that found in the non-reserve areas.
The researchers found that the smaller species of parrotfish were smaller inside the reserve. This is due to
the fact that predators can eat fish that are up to 60 percent of their jaw size, combined with the parrotfish’s
nocturnal resting in vulnerable reef locations, the fish is a much easier target for predators. The reserves
had the opposite effect on the larger species of parrotfish because of the released pressure from fishing on
these populations. The macroalgae covering of the coral reefs was reduced by 4 fold because of over
grazing by large fish. This is compared to the non-reserve reef where there were no fluctuations in cover.
However, the reduction in this cover is actually beneficial to the survival of the corals. The benefits of this
type of conservation, as well as the impacts this kind of preservation may have on the existing ecosystems
are still being discovered. Each reef will certainly be affected differently due to the circumstances that
surround the reef, making the evaluation of each reef and the impact these marine protected areas have on
the reef more difficult for researchers
Another method for preserving coral reefs is to build man made reefs. These reefs are used to
cultivate and increase fish populations. Fish larvae return to the reef habitat for the duration of their lives,
and, since they are active swimmers, choose specifically where to settle on the reef. Discovering why fish
settle in a particular habitat is essential for promoting life in an artificially constructed reef. Simpson et al ()
discovered that settlement was more likely to occur in some sites than in others because of sounds produced
in the reef.
Researchers constructed 24 patch reefs from dead coral rubble off of Lizard Island on the Great
Barrier Reef. They then placed underwater speakers that broadcast reef noise, mostly made by fish and
shrimp, at half of these sites. It was found that most of the larvae settled near the loud speakers rather than
in quieter areas. A month later the constructed reefs were used to distinguish which fish preferred higher or
lower frequencies. It was discovered that the apogonids settled at both the high and low frequency reef
systems but that the pomacentrids were attracted primarily to the high frequency reefs. The studies provide
evidence that supports the authors’ idea that fish use sound in order to orientate themselves to and select a
reef to inhabit. The studies also suggest that human interference with underwater noises could potentially
disrupt the settlement process. Examples of potentially harmful interference are the noises from ships and
underwater drilling. Using this information these constructed reefs could potentially be finely tuned to
attract local reef fishes. If this were to occur, man made reefs could be used as centers of tourism, ensuring
the protection of the natural habitat.
The only way to ensure the future of this ecosystem is to protect it now. The increase of marine
protected areas and further knowledge of the problems facing the ecosystem are beneficial. Scientists are
gearing towards creating preservation areas on a similar scale as terrestrial conservation efforts. Coral reefs
that are repeatedly damaged by human activities can eventually be destroyed. Roberts et al. (2002) intended
to explore the potential consequences of this reef degradation on biodiversity in order to heighten
conservation efforts. Researchers recreated a reef ecosystem using taxa represented reef biodiversity on a
global scale. By using this global scale the researchers were able to calculate the average threat to all coral
reefs. The data proved that 3 of the 4 taxa of marine species are not resistant to extinction because they are
restricted-range species. If any particular area of reef was extremely degraded it could lead to a range
specific extinction of many species. It was found that areas that contained the greatest species richness were
much more greatly threatened by human impacts than areas of relatively little species richness.
Terrestrial biodiversity hotspots are determined on the basis of endemism and the threats that are
facing them. The researchers identified 18 of the richest centers of endemism. Covering only 35 percent of
the world’s coral reefs. Even though these centers cover a relatively small portion of the world’s reefs, they
contain almost 70 percent of the world’s restricted-range species. The protection of these reefs would be
highly effective in protecting species abundance. Of these 18 hotspots, 14 are adjacent to terrestrial
biodiversity hotspots. The proposed extension of terrestrial conservation efforts to the seas that surround
them would increase the hope of preserving the reef ecosystems and the marine biodiversity that inhabit
these areas. The researchers are calling for equal attention to be paid to marine protected areas as terrestrial
areas of preservation. The increase of marine protected areas could hold the potential to save these vital
resources and also provide scientists with more information on how to protect marine ecosystems.
As global coral reefs continue to decline, science has provided new hope in long term preservation
efforts. As we continue to gather a greater understanding of these ecosystems, new solutions will continue
to emerge. Along with advances in reef technology, scientists continue to look at newly discovered
relationships within the coral reefs for answers. It is only through the immediate preservation of this
resource that future efforts will be possible. While research behind marine protected areas is certainly still
in infancy, it is seemingly the best solution to preserving the coral reefs. Then through the study of these
areas may scientists learn the intricate workings of the reef ecosystem. In the future our advanced
knowledge of the ocean can only increase our ability to protect and preserve it.
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